Self-regenerating air dryer and purifier

ABSTRACT

An air drying system includes a first air dryer that receives ambient air and provides as output exceptionally dry air having a moisture concentration of approximately 16 ppm or below, a second air dryer that receives ambient air and provides as output exceptionally dry air having a moisture concentration of approximately 16 ppm or below, and a valve coupled to and selectively switching between output from the air dryers to provide exceptionally dry air, where one of the first and second air dryers is automatically regenerated while the valve switches to provide exceptionally dry air from an other one of the first and second air dryers. The air dryers may remove moisture from ambient air by cooling the ambient air to approximately −57° C. Each of the air dryers may include a heat sink section, a cooling section (possibly with cooling elements), and an air flow section.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional App. No. 62/012,438, filed Jun. 16, 2014, entitled “SELF-REGENERATED DRYER AND PURIFIER SYSTEM”, which is incorporated herein by reference.

TECHNICAL FIELD

This application relates to the field of air drying systems and, more particularly, to the field of air drying systems that provide exceptionally dry air having a moisture concentration of approximately 16 ppm or below (corresponding to a relative humidity of 0.1% or below at ambient pressure and temperature) for use in analytic instruments.

BACKGROUND OF THE INVENTION

Many analytic instruments require a constant flow of relatively dry air for proper operation. Although it is possible to use compressed dry air provided in a tank, it is usually more cost effective to use ambient air that is dried prior to being injected into the analytic instrument. However, some analytic instruments, such as ion mobility spectrometers, usually require exceptionally dry air for operation (e.g., approximately a moisture concentration under 16 ppm or below, corresponding to a relative humidity of 0.1% at ambient pressure and temperature). Many conventional single stage air dryers cannot remove enough moisture from ambient air to achieve this desired level of relative humidity. In such cases, two stage air dryers may be used, such as the ambient air dryer disclosed in U.S. Pat. No. 5,405,781 to Davies, et al., which is incorporated by reference herein, where a first stage cools incoming ambient air to between 2° C. and 6° C. and a second stage that receives the cooled ambient air dehumidifies the air using a desiccant, such as calcium sulphate.

A difficulty with a two stage air dryer such as that disclosed by Davies is that having an additional stage adds complexity to the device. In addition, the desiccant has a finite life span and must be replaced periodically for the air dryer to work properly. This additional maintenance adds to the cost of operating the system and improper maintenance (i.e., failure to timely replace the desiccant) can cause a corresponding analytic instrument to not work properly.

Accordingly, it is desirable to provide a low maintenance and reliable single stage air drying system that can convert ambient air into exceptionally dry air with a moisture concentration of approximately 16 ppm or below (corresponding to a relative humidity of 0.1% or below at ambient pressure and temperature) for use in analytic machines.

SUMMARY OF THE INVENTION

According to the system described herein, an air drying system includes a first air dryer that receives ambient air and provides as output exceptionally dry air having a moisture concentration of approximately 16 ppm or below, a second air dryer that receives ambient air and provides as output exceptionally dry air having a moisture concentration of approximately 16 ppm or below, and a valve coupled to and selectively switching between output from the air dryers to provide exceptionally dry air, where one of the first and second air dryers is automatically regenerated while the valve switches to provide exceptionally dry air from an other one of the first and second air dryers. The air dryers may remove moisture from ambient air by cooling the ambient air to approximately −57° C. Each of the air dryers may include a heat sink section, a cooling section, and an air flow section. The cooling section may include a plurality of cooling elements. The cooling elements may be thermoelectric cooling elements. The thermoelectric cooling elements may be Peltier coolers. The air flow section may include an air chamber that receives ambient air at one end thereof and outputs exceptionally dry air at an other end thereof. The air chamber may include a plurality of beads. The beads may be metal or glass. The air drying system may also include a third air dryer, coupled to the valve, that receives ambient air and provides as output exceptionally dry air having a moisture concentration of approximately 16 ppm or below.

According further to the system described herein, operating an air drying system includes activating a first air dryer that receives ambient air and provides as output exceptionally dry air having a moisture concentration of approximately 16 ppm or below, causing a valve to provide output from the first air dryer, monitoring the first air dryer to detect when the first air dryer needs to be regenerated, and, in response to the first air dryer needing regeneration, activating a second air dryer that receives ambient air and provides as output exceptionally dry air having a moisture concentration of approximately 16 ppm or below and causing the valve to provide output from the second air dryer while the first air dryer is being regenerated. The air dryers may remove moisture from ambient air by cooling the ambient air to approximately −57° C. Each of the air dryers may include a heat sink section, a cooling section, and an air flow section. The cooling section may include a plurality of cooling elements. The cooling elements may be thermoelectric cooling elements. The thermoelectric cooling elements may be Peltier coolers. The air flow section may include an air chamber that receives ambient air at one end thereof and outputs exceptionally dry air at an other end thereof. The air chamber may include a plurality of beads. The beads may be metal or glass. Operating an air drying system may also include activating a third air dryer, coupled to the valve, that receives ambient air and provides as output exceptionally dry air having a moisture concentration of approximately 16 ppm or below.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the system are described with reference to the several figures of the drawings, noted as follows.

FIG. 1 is a schematic illustration of an air drying system according to an embodiment of the system described herein.

FIG. 2 is a two-dimensional schematic illustration of an air dryer according to an embodiment of the system described herein.

FIG. 3 is a three-dimensional schematic illustration of an air dryer according to an embodiment of the system described herein.

FIG. 4 is a schematic illustration of an air flow chamber with beads according to an embodiment of the system described herein.

FIG. 5 is a flow diagram illustrating operation of an air drying system according to an embodiment of the system described herein.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

Referring to FIG. 1, an air drying system 100 includes a first air dryer 102 and a second air dryer 102′ that provide exceptionally dry air (e.g., air with a moisture concentration of approximately 16 ppm or below, corresponding to a relative humidity of 0.1% or below at ambient pressure and temperature) to an analytic instrument 104. The analytic instrument 104 can be any analytic instrument that uses exceptionally dry air, such as an implant mobility spectrometer. The first air dryer 102 has a first inlet 106 for receiving ambient air and the second air dryer 102′ has a second inlet 106′ for receiving ambient air. The first inlet 106 and the second inlet 106′ are separate, but may receive ambient air from generally the same area or from different areas.

Exceptionally dry air that is output from the air dryer 102 is provided to a first conduit 108 while exceptionally dry air that is output from the air dryer 102′ is provided to a second conduit 108′. The conduits 108, 108′ are coupled to a three-way valve 112 that selectively provides exceptionally dry air from one of the conduits 108, 108′ to the analytic instrument 104 according to a position of the valve 112. Operation of the air drying system 100, including actuation of the valve 112 to select a particular one one the conduits 108, 108′ (and thus select one of the air dryers 102, 102′) is described in more detail elsewhere herein.

Referring to FIG. 2, the air dryer 102 is shown as having a heat sink section 132, a cooling section 134, and an air flow section. The heat sink section 132 may be implemented using conventional heat sink technology, such as using a plurality of fins made out of an appropriate metal, such as aluminum. Any other appropriate heat sink mechanism may be used that can draw heat away from the air dryer 102.

The cooling section 134 includes a plurality of cooling elements 142 a-142 c that cool down interior portions of the air dryer 102 to approximately −57° C., a temperature at which the maximum relative humidity in ambient air cannot exceed approximately 0.1%. When ambient air is cooled to this temperature, nearly all the moisture in the air condenses, with the resulting cooled air having a moisture concentration of no more than approximately 16 ppm or below (corresponding to a relative humidity of 0.1% or below at ambient pressure and temperature). Note that other cooling levels are possible, with different temperatures resulting in different relative humidity values. For example, at approximately −35C, the maximum relative humidity is approximately 1.0%. Of course, the cost increases as the amount of cooling increases, so there is a tradeoff between cost and amount of cooling and acceptable relative humidity. It has been found that a relative humidity of approximately 0.1% results in acceptable operation of an ion mobility spectrometer while, at the same time, being reasonably attainable with respect to cost and power consumption for cooling elements to provide the needed temperature levels. In an embodiment herein, the cooling elements 142 a-142 c are provided by Peltier coolers, although any other type of cooling element may be used, including any appropriate thermoelectric coolers. Note that, in addition to moisture, the air dryer 102 may also trap any other impurities having a freezing point above approximately −57° C.

The air flow section 136 includes an air flow chamber 144, which is shown in FIG. 2 perpendicular to a direction of flow. The cooling section 134 cools the air flow chamber 144 to approximately −57° C. Ambient air at room temperature flows in one end of the air chamber and exceptionally dry air (that has been cooled) flows out of an other end of the air chamber 144. In an embodiment herein, moisture in the ambient air condenses within the air chamber 144.

Referring to FIG. 3, the air dryer 102 is shown in three dimensions with a portion being cut away for illustrative purposes. The heat sink section 132 is shown with fins. The cooling elements 142 a-142 c are shown as being embedded within the cooling section 134. The air chamber 144 is provided in a portion of the air flow section 136 that is adjacent (or nearly adjacent) to the cooling section 134.

Referring to FIG. 4, in an embodiment the air chamber 144 is provided with a plurality of beads 152, which increase surface area for effective condensation. The beads 152 may be made out of metal, glass, or any appropriate material. The beads 152 may be any appropriate size, and may be different sizes. In one embodiment, the size of the beads may be optimized to provide a maximum, or near maximum surface area for effective condensation. Note that the surface area of the beads 152 available for effective condensation equals the total surface area of all of the beads 152 minus portions of the surface area of the beads 152 corresponding to contact between the beads 152 and contact between an inside surface of the air chamber 144 and the beads 152.

Referring to FIG. 5, a flow diagram 170 illustrates operation of the air drying system 100. Processing begins at a first step 172 where the air dryer 102 is activated. Activating the air dryer 102 at the step 172 includes turning on the air dryer 102 and adjusting the valve 112 to cause the output flow from the air dryer to flow, via the conduit 108, to the analytic instrument 104. Following the step 172 is a test step 174 where it is determined if regeneration of the air dryer 102 is needed. Since the air dryer 102 is removing moisture from ambient air by effective condensation, then after a certain amount of time, condensate within the air dryer 102 accumulates to a point where operation of the air dryer is adversely affected. The air dryer 102 continuously accumulates condensate during operation and, at some point, the amount of condensate inhibits operation.

If it is determined at the test step 174 that regeneration is not needed, then control transfers from the test step 174 back to the test step 174 to continue to poll. Otherwise, control transfers from the test step 174 to a step 176 where the air dryer 102 is deactivated and regeneration of the air dryer 102 is begun. In an embodiment herein, regeneration of the air dryer 102 includes heating the air dryer to remove the frozen condensate, although any other appropriate techniques may be used to remove the condensate from the air dryer (e.g., manually removing the ice formed in the air chamber 102). Note that regeneration of the air dryer 102 does not require replacing any components (such as desiccant) and that the entirety of the air dryer 102 is reusable after regeneration.

Following the step 176 is a step 178 where the air dryer 102′ is activated. Note that the steps 176, 178 may be performed in parallel and/or nearly simultaneously (or in a different order) so that the analytic instrument 104 is never without a supply of exceptionally dry air. Activating the air dryer 102′ at the step 178 is similar to activating the air dryer 102 at the step 172, discussed above. Following the step 178 is a test step 182 where it is determined if the air dryer 102′ needs to be regenerated. The test at the step 182 is similar to the test at the step 174, described above. If regeneration is not needed, control loops back to the step 182 to continue polling. Otherwise, control transfers from the step 182 to a step 184 where the air dryer 102′ is deactivated and regenerated. The step 184 is similar to the step 176, described above. Following the step 184, control transfers back to the step 172 for another iteration. As with the steps 176, 178, the steps 184, 172 may be performed in parallel and/or nearly simultaneously (or in a different order) so that the analytic instrument 104 is never without a supply of exceptionally dry air.

Note that the fact that regeneration of the air dryers 102, 102′ may be performed completely automatically (e.g., by heating the air dryers 102, 102′) allows the system to run continuously through may cycles. In contrast, a system that uses a desiccant for drying air or otherwise requires replacement of at least some components periodically cannot run automatically through a number of cycles but, instead, requires periodic human intervention to facilitate operation. Note also that, generally, while one of the air dryers 102, 102′ is drying ambient air and providing exceptionally dry air to the analytic device 104, the other one of the air dryers 102, 102′ may be regenerated. In some embodiments, it is possible to use more than two air dryers in parallel, with an appropriate valve to switch between the plurality of air dryers.

Various embodiments discussed herein may be combined with each other in appropriate combinations in connection with the system described herein. Additionally, in some instances, the order of steps in the flow diagrams, flowcharts and/or described flow processing may be modified, where appropriate.

Other embodiments of the invention will be apparent to those skilled in the art from a consideration of the specification or practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims. 

What is claimed is:
 1. An air drying system, comprising: a first air dryer that receives ambient air and provides as output exceptionally dry air having a moisture concentration of approximately 16 ppm or below; a second air dryer that receives ambient air and provides as output exceptionally dry air having a moisture concentration of approximately 16 ppm or below; and a valve coupled to and selectively switching between output from the air dryers to provide exceptionally dry air, wherein one of the first and second air dryers is automatically regenerated while the valve switches to provide exceptionally dry air from an other one of the first and second air dryers.
 2. An air drying system, according to claim 1, wherein the air dryers remove moisture from ambient air by cooling the ambient air to approximately −57° C.
 3. An air drying system, according to claim 2, wherein each of the air dryers includes a heat sink section, a cooling section, and an air flow section.
 4. An air drying system, according to claim 3, wherein the cooling section includes a plurality of cooling elements.
 5. An air drying system, according to claim 4, wherein the cooling elements are thermoelectric cooling elements.
 6. An air drying system, according to claim 5, wherein the thermoelectric cooling elements are Peltier coolers.
 7. An air drying system, according to claim 3, wherein the air flow section includes an air chamber that receives ambient air at one end thereof and outputs exceptionally dry air at an other end thereof.
 8. An air drying system, according to claim 7, wherein the air chamber includes a plurality of beads.
 9. An air drying system, according to claim 8, wherein the beads are one of: metal and glass.
 10. An air drying system, according to claim 1, further comprising: a third air dryer, coupled to the valve, that receives ambient air and provides as output exceptionally dry air having a moisture concentration of approximately 16 ppm or below.
 11. A method of operating an air drying system, comprising: activating a first air dryer that receives ambient air and provides as output exceptionally dry air having a moisture concentration of approximately 16 ppm or below; causing a valve to provide output from the first air dryer; monitoring the first air dryer to detect when the first air dryer needs to be regenerated; and in response to the first air dryer needing regeneration, activating a second air dryer that receives ambient air and provides as output exceptionally dry air having a moisture concentration of approximately 16 ppm or below and causing the valve to provide output from the second air dryer while the first air dryer is being regenerated.
 12. A method, according to claim 11, wherein the air dryers remove moisture from ambient air by cooling the ambient air to approximately −57° C.
 13. A method, according to claim 12, wherein each of the air dryers includes a heat sink section, a cooling section, and an air flow section.
 14. A method, according to claim 13, wherein the cooling section includes a plurality of cooling elements.
 15. A method, according to claim 14, wherein the cooling elements are thermoelectric cooling elements.
 16. A method, according to claim 15, wherein the thermoelectric cooling elements are Peltier coolers.
 17. A method, according to claim 13, wherein the air flow section includes an air chamber that receives ambient air at one end thereof and outputs exceptionally dry air at an other end thereof.
 18. A method, according to claim 17, wherein the air chamber includes a plurality of beads.
 19. A method, according to claim 18, wherein the beads are one of: metal and glass.
 20. A method, according to claim 11, further comprising: activating a third air dryer, coupled to the valve, that receives ambient air and provides as output exceptionally dry air having a moisture concentration of approximately 16 ppm or below. 